| The biological Characteristics and esterase isozyme zymograms of the pathogenic fungus causing Fusarium wilt of cotton in Anhui were studied systematically, the physiological and biochemical mechanism in resistance of transgenic cotton to Fusarium wilt and Verticillium wilt was analyzed as an emphasis, and inhibition of Bacillus subtilis and Trichoderma harzianum against the pathogens of the two diseases and the inhibitive mechanism were investigated in this paper. The main results were as follows. 1. Biological characteristics and esterase isozyme analysis of the pathogenic fungus of cotton Fusarium wilt in Anhui The effects of temperature, pH, carbon and nitrogen sources on the mycelium growth, dry mycelium weight and conidium production of Fusarium oxysporum f. sp. vasinfectum (Atk.) Synder & Hansen, the pathogenic fungus causing Fusarium wilt of cotton in Anhui, were studied, and the esterase (EST) isozyme analysis of the 15 tested isolates was conducted. The results showed that for the mycelial growth of F. oxysporium f. sp. vasinfectum, the range of temperature was between 10℃ to 35℃, the optimum being 25℃, and the range of pH was 4~10, the optimum being 6~7. Sucrose was the best carbon source for the mycelium growth of the fungus. But it was junior to soluble starch for the increase of the net weight of mycelium. Among the tested nitrogen sources, urea was the best, next was sodium nitrate, and then ammonium nitrate, for the mycelium growth and conidial production of the causal organism. The results also indicated that there was obvious difference in the main enzyme zones of EST isozyme zymograms among the 15 tested isolates, and they could be divided into four types. The type of EST isozymes was related to the pathogenicity. It was suggested that the electrophoresis of EST isozyme analysis might be useful for distinguishing different pathogenicity types of F. oxysporium f. sp. vasinfectum. 2. Studies on mechanism of physiological and biochemical resistance to Verticillium wilt and Fusarium wilt of transgenic cottons and general ones (1)Comparison of the four defensive enzyme activities between the transgenic adult cottons and general ones after inoculation with Verticillium dahliae and F. oxysporium f. sp. vasinfectum in farmland The extracellular enzyme activities of the two pathogenic fungi and the seedling and adult resistance of four cotton cultivars to Verticillium wilt and Fusarium wilt of cotton were investigated. Meanwhile, the physiological and biochemical changes were studied after inoculation with V. dahliae and F. oxysporium f. sp. vasinfectum in order to clarify the physiological and biochemical resistance mechanism of transgenic cotton and general cotton to Verticillium wilt and Fusarium wilt of cotton. The results were as following: Cotton cultivars were inoculated with V. dahliae and F. oxysporium f. sp. vasinfectum with the conidium-pouring of the wound seedling's roots and the diseased plant rate was investigated at the 30th day after inoculation. Four cotton cultivars were susceptible in seeding, but there were significant difference on the diseased plant rates among cultivars after inoculation with F. oxysporium f. sp. vasinfectum . The diseased plant rate of Wanza 40 was the highest and Guokang 1 was the lowest, while others cultivars were between Wanza 40 and Guokang 1. After inoculating with V. dahliae, four cotton cultivars were susceptible in seedling, but there were significant difference on the diseased plant rate among cultivars. Simian 3 was the highest and Zhongmian 29 was the lowest, while others cultivars were between Simian3 and Zhongmian 29. Cotton cultivars were inoculated with V. dahliae and F. oxysporium f. sp. vasinfectum with the root-hurting and conidium-pouring method in adult stage. The result showed that Zhongmian 29, Guokang 1 were resistant cultivars and the resistance indexes were 12.9, 12.3 respectively. While Wanza 40, Simian 3 were susceptible cultivar and the resistance index were only 6.2, 2.5 respectively. Four defensive enzymes' activi... |
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